| 1 | Dumeril’s boa |
Southern Madagascar’s main boa, and once extremely popular in captivity worldwide. These days, their numbers are fewer, due to falling wild populations, but one benefit in their prime was how easy they were to feed.
Dumeril’s boas are simple mammal-eaters, and rats and mice are more than satisfactory. This species reaches 259cm, and their confirmed wild prey include southern bamboo lemurs. They have 2 fellow boas on their island, the Madagascan ground and tree boas, which form a highly isolated 3-member branch of the boa family worldwide. They diverged from boa constrictors tens of millions of years ago, despite a close resemblance.
Dumeril’s boas are ambush predators and would fail if they tried anything else, as they’re too cumbersome to stalk a lemur stealthily. But they do produce an exceptional burst of speed while lunging, which is difficult for a rat to dodge. It’s also possible that they hunt bats. Dumeril’s boas have been spotted in caves in Tsimanampesotse National Park, so they may copy Cuban boas, which seize bats in caves when they fly out in their thousands. Common species nearby include the Malagasy mouse-eared bat and Madagascar flying fox.
| 2 | Monocled cobra |
Thailand’s most common cobra species. Monocled cobras measure 100-150cm and are identifiable by the single round marking on their hood, not double like an Indian cobra. A monocled cobra can 1) kill you, 2) leave you disfigured, 3) deliver a lucky dry bite, or 4) paralyse you for 4 days, before a full and complete recovery. Many scenarios are possible with this roulette wheel of a snake.
Like most cobras, Naja kaouthia is extremely flexible. They can enjoy the feathers of a bird, scales of a snake, and sliminess of a frog, but a 2011 study found that the fur of a mammal tickles their fancy the most. Mammals contributed 75.8% of prey in wild monocled cobras, followed by birds’ eggs at 11.3% and reptiles at 8.0%. This involved 93 prey taken from 75 cobras, in Thailand’s Singburi province.
Most brutally, several monocled cobras contained multiple nestling mice, as though they’d visited their den and gobbled up several at once, possibly by invading their winding burrows. Living alongside this species is terrifying, as they commonly invade gardens, kitchens and supermarkets in Bangkok. But a rare benefit is that they hoover up rodents for farmers, reducing the economic damage they cause.
| 3 | Crossed pitviper |
The Bothrops pitviper family has 30 members in Brazil, specialising in tissue necrosis and swelling. The most mammal-loving of these nightmares is the crossed pitviper, resident of southern Brazil. 2 studies analysed the crossed pitviper’s diet, and both detected 100% mammals. In one, rats and mice comprised 80.8%, and this study had a strong sample size, with 182 crossed pitvipers examined.
Unlike a monocled cobra, crossed pitvipers don’t lurk in crop fields and helpfully eat rodent pests. Nor do they inhabit southern Brazil’s dark, spooky Atlantic forests (like a jararacussu). Instead, this is a species of open cerrado grassland, sometimes bordering old dirt roads, often close to villages. They live a lazy lifestyle, moving just a few metes per day.
While peaceful, with swaying grass and splendid views, these grasslands are in reality a constant battleground, populated by rival animals forced to take up arms. There’s the mice and rats, skilfully avoiding the crossed pitvipers determined to eat them, and there’s watchful burrowing owls determined to eat the crossed pitviper, which must avoid their gaze using a delicate balancing act. Crossed pitvipers have been found in burrows with tiny entrances, just 10cm wide. It’s almost certain that they swallow the inhabitants before taking up residence.
| 4 | Black mamba |
It’s mainly the rapid-acting, paralysing venom that gets the attention with black mambas. This notorious African terror can kill you in under one hour, but they’re interesting in more subtle ways too. For example, black mambas completely avoid eating reptiles and amphibians, turning up their noses if presented with them in captivity. Instead, they eat 81.48% mammals and 14.81% birds, according to a study from Namibia and eastern Transvaal. Their diet is completely different to their fellow unstoppable serpent icon, the king cobra, which mainly swallows fellow snakes, venom gland and all. Black mambas have a milder menu of tree squirrels, Namaqua rock rats and red veld rats.
Black mambas actually rank among the top ten longest snakes on Earth, perhaps reaching 4 metres. But unlike a rock python, there’s no chance of one eating a human child, as their bodies are too thin. Black mambas stick to relatively small meals. The real worry is their hyper-alert, defensive personality.
Black mambas aren’t quite the lord of Africa, as they’ve been found in the stomachs of Nile crocodiles, and reportedly flee when they see one stomping out of a river.
| 5 | Tzabcan rattlesnake |
The ruling rattlesnake of Mexico’s Yucatán peninsula, Mexico’s safest state, home to ancient pyramids which some believe were built by aliens, and not far from the dino-destroying asteroid impact crater. Central American coral snakes are another venomous snake found here, but they focus on fellow snakes, while Tzabcan rattlesnakes eat exclusively mammals. A 2020 study found a diet consisting of 100% mammals, across 28 prey found in 50 different Crotalus tzabcan. Rodents form a large chunk of their prey, including the Toltec cotton rat and Gaumer’s spiny pocket mouse.
Tzabcan rattlesnakes reach a maximum of 181.8cm, with males slightly longer. Mammal-exclusive diets aren’t guaranteed for rattlesnakes. Rock rattlesnakes of Arizona eat over 50% reptiles, and just 20% mammals, whereas west and east diamondbacks eat over 90% mammals, like Crotalus tzabcan.
As they inhabit a peninsular, nobody’s forcing you to enter their realm. You can keep driving straight ahead rather than taking the road left, and not risk crossing the Yucatán heartlands they control with an iron fist. But as you plough deeper into central America, there’s no avoiding snakes forever. Sooner or later, you’ll come fast to face with a hissing serpent, possibly one of Crotalus tzabcan’s mammal-eating mates like the Central American rattlesnake (Crotalus simus).
| 6 | Reticulated python |
It may have occurred to you that humans are mammals too, but rest assured that most on this list aren’t eyeing you up, imagining you covered with Walmart-brand barbeque sauce. Most are simply too small, but the one dangerous exception is the reticulated python, Earth’s longest surviving snake, among 3900 worldwide. Reticulated pythons eat mainly mammals because they’re the only creatures consistently large enough to satisfying their enormous needs. Monkeys and wild boar are on the menu, while an Asian rice frog would be horribly unsatisfactory.
In 2022, an Indonesian woman was killed and swallowed by a reticulated python, though her body was quickly rescued, allowing for a funeral (and the snake to be killed). There was a sort of heartwarming story in 2011 about a young Cambodian boy keeping one as beloved bedroom pet for over 5 years, but internet commenters believed that when it stretched its body out on the bed, it was actually measuring him.
The duo were eventually separated, and there’s no doubt that reticulated pythons won’t hesitate to hunt human children. Like a great white shark, it depends on how hungry they are at the time, whether they’ve had a satisfying meal recently.
| 7 | Steppe ratsnake |
The most common of the 18 member Elaphe ratsnake genus. This species inhabits a swathe of Eurasia, from Ukraine to Korea, and is harmless to humans. With favourite prey including the Korean field mice and brown rat, the steppe ratsnake is a mammal-eating machine. A 2022 study confirmed these tendencies, as among 79 individual Elaphe dione examined, every single prey discovered was a mammal.
Neither too fast nor too grindingly slow, steppe ratsnakes roam the countryside endlessly and unceasingly, searching for trodden vegetation which may indicate a well worn mammal trail. Combined with constant tongue flecking, and a high sensitivity to small mammal scents, it’s virtually guaranteed that steppe ratsnakes will find a rat sooner or later. Elaphe dione is a constrictor, albeit a relatively inefficient one, relying more on skillful grappling. Rustling bushes and strangely swaying grass may indicate that a steppe ratsnake is nearby.
Having a mammal-heavy diet makes the steppe ratsnake relatively easy to keep in captivity. You can practically fling them a defrosted mouse over your shoulder while you watch TV to great success.
| 8 | Asp viper |
France’s main venomous snake isn’t just a mammal obsessive, but gains 98% of its meals from voles, according to one study. This occasionally fatal species inhabits the lower 80% of France, southern Switzerland, and most of Italy. They particularly like grassy meadows, lurking in hedges on their borders.
Asp vipers experience an ontogenetic change in their diet, eating 81% reptiles as a newborn, before mammals push everything else aside in adulthood. Adults don’t abandon reptiles completely, but love small, scurrying creatures that share their grassy habitats. A study from Central Italy’s Tolfa mountains found a diet of 81.4% mammals, especially the common shew and the house mouse. Weirdly, a study from northern Italy found that they ignored the local mice: the wood mouse and striped field mouse. Their favourites were the Savii’s pine vole, in line with the French studies, and lesser white-toothed shrew.
Either way, it’s in the same ballpark: small, traditional European mammals, compared to the neighbouring grass snake which mainly eats frogs. Asp viper bites trigger swelling, blistering and abdominal pain, and have neurotoxic properties in certain regions like Nice.
| 9 | Ladder snake |
Spain’s top mammal-eating snake. Montpellier snakes are flexible vacuum cleaners, while horseshoe whipsnakes eat reptiles, but one study found that ladder snakes ate 87.2% mammals, followed by a smattering of birds at 11.7%.
Ladder snakes measure 100cm, maximum 160cm, and are non-venomous, though occasionally snappy. They were named for the ladder patterns down their spine, and inhabit dry countryside areas like dirt tracks and olive plantations. The Mediterranean pine vole is a particular favourite prey. Both this and horseshoe whipsnakes are invasive species on Ibiza, but only the latter is considered dangerous, as they’re wreaking havoc on the native Ibiza wall lizard, while the ladder snake mostly ignores them.
Ladder snakes are not only Spain’s top mammal-muncher, but go to extreme lengths to get them. Ladder snakes ambush mice families while they sleep, by finding burrow entrances and slithering through the underground tunnels, like a basilisk slithering through plumbing. When they find the resting chamber, ladder snakes can swallow several sleeping mice at once, helpless to defend themselves. However, they’re not completely doomed. The more dim-witted mice will be swallowed instantly, but faster, more inventive mice may dart aside, run over the ladder snake’s back, or inflict a quick gnawing wound. Sometimes, there’s no escape, as they find themselves backed into a dead end tunnel.
| 10 | Coastal taipan |
The two taipans, the inland and coastal taipan, are easily the most mammal-obsessed of the many venomous Australian snakes. Inlands live in dry clay cracks deep within the outback, whereas coastal taipans inhabit civilised areas along the coast like fields and woods, including near Sydney. They’re fast and agile, and capable of injecting a jabbing bite and vanishing down a hill before you have any time to react.
According to a study on wild coastal taipans, 18 prey were mammals versus just 1 bird. Their speed is a natural consequence, as gnawing rodents are capable of killing coastal taipans in a few seconds, with a lucky strike. Their neurotoxic venom is also useful, paralysing the rat’s limbs, and removing it from the fight.
Coastal taipans completely ignore frogs, leaving them to red-bellied black snakes, and ignore reptiles, leaving them to small-eyed snakes. Coastal taipans are active foragers, usually slithering with their head raised. When they encounter a rodent, they’ve been observed to freeze for a second, before unleashing their successive rapid strikes. Confirmed prey in their diet include dusky field rats, pale field rats, and long-nosed bandicoots.